Left and right sum differences

Array Prefix Sum

87.9% acceptance

Feb 25, 2026

1244

115

You are given a 0-indexed integer array nums of size n. Define two arrays leftSum and rightSum where: leftSum[i] is the sum of elements to the left of the index i in the array nums. If there is no such element, leftSum[i] = 0. rightSum[i] is the sum of elements to the right of the index i in the array nums. If there is no such element, rightSum[i] = 0. Return an integer array answer of size n where answer[i] = |leftSum[i] - rightSum[i]|.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn left_right_difference(nums: Vec<i32>) -> Vec<i32> {
    let total: i32 = nums.iter().sum();
    let mut left = 0i32;
    let mut result = Vec::with_capacity(nums.len());
    for &x in &nums {
      let right = total - left - x;
      result.push((left - right).abs());
      left += x;
    }
    result
  }
}